Oscillating actuator

ABSTRACT

A swinging actuator has an output shaft rotatably supported by a support member, a driving source for rotate-driving the output shaft, and an output arm, whose base end portion is connected and fixed to an end surface of the output shaft. A portion to be driven is driven by the end portion of the output arm. The swinging actuator comprises a screw hole provided in a portion, which is positioned off the center of rotation of the output shaft, a through hole formed in the base end portion of the output arm, a connecting screw screwed into the screw hole in a state in which the connecting screw is inserted into the through hole, and an engagement portion provided between a part, which is positioned off the through hole and in the end portion of the output arm, and a part, which is off the screw hole and in the end surface of the output shaft.

TECHNICAL FIELD

The present invention relates to a selecting actuator, which isincorporated into, for example, an electric drive apparatus for atransmission, for displacing a shift shaft for a gear unit in an axialdirection.

BACKGROUND ART

A manual transmission is used as an automotive transmission. However, inrecent years, there have been proposed various kinds of automotivetransmissions each for automatically switching a gear unit and forautomatically disconnection of a clutch. International Publication No.WO01/31234A1 discloses an electric drive apparatus for changing gearsconstituting a gear unit in such an automotive transmission.Hereinafter, the electric drive apparatus for a transmission accordingto the International Publication is described by referring to FIGS. 6 to8.

A mission case 1 is a case that incorporates a gear unit similar to amanual transmission. A tip end portion 3 of a shift shaft 2 for changinga gear ratio of this gear unit projects from a side surface of themission case 1. A male spline portion 4 is formed in a middle part ofthis tip end portion 3. The male spline portion 4 is spline-engaged witha spline tube 5, on the inner surface of which a female spline isformed. An engagement piece 7, in the outer peripheral surface of whichan engagement groove 11 is formed, is connected to a part that is closerto the tip of the tip end portion 3 protruding from the spline tube 5.

The operation shift shaft 2 is displaced in an axial direction (afront-rear direction of the sheet of FIG. 6, an up-down direction of thesheet of FIG. 7) in a selecting operation, and rotates in a shiftoperation. Incidentally, the selecting operation is an operation ofdisplacing a shift lever in a direction of width of a vehicle in anordinary manual floor shift car to thereby select a gear for changing aspeed. On the other hand, the shifting operation is another operation ofdisplacing the shift lever in a front-back direction of the vehicle tothereby connect a synchromesh mechanism corresponding to the selectedgear.

Hereinafter, the selecting operation and the shifting operation aredescribed in detail. A gear unit realizing six kinds of transmissionstates, which are five forward ones (first to fifth speed levels) and arearward one (R), as shown in FIG. 9, are considered herein.

In the selecting operation, one of three kinds of positions, which areboth lateral end positions and a laterally central position shown inFIG. 9, is selected. In this selecting operation, the synchromeshmechanisms are maintained in a free state. Thus, a neutral state ismaintained, so that no speed change state occurs. In the shiftingoperation, the shift lever is displaced from one of the three kinds ofpositions in the neutral state in one direction (an upward or downwarddirection shown in FIG. 9). Consequently, one of the synchromeshmechanisms is brought into a connected state, so that one of speedchange states occurs. Incidentally, according to the InternationalPublication No. WO01/31234A1, a selecting actuator 8, which is aswinging actuator, is provided between an outer surface of the missioncase 1 and the engagement piece 7 so as to displace the shift shaft 2 inthe axial direction in the selecting operation.

As shown in FIG. 8, the selecting actuator 8 has a selecting electricmotor 9, and a multiple thread worm gear 10 rotate-driven by an outputshaft of the selecting electric motor 9. The multiple thread worm gear10 meshes with a worm wheel 11. An output shaft 12 serving as the centerof rotation of the worm wheel 11 is connected and fixed to a base endportion of a swinging arm 13. The swinging arm 13 rotates together withthe worm wheel 11. An engagement convex portion 14 formed on one sidesurface of the tip end portion (the top surface of the left end portion,as viewed in FIG. 6) of the swinging arm 13 engages with the engagementgroove 6 to thereby allow the shift shaft 2 to be displaceable.

On the other hand, a shifting actuator 16 serving as a direct actingactuator for rotating the shift shaft 2 is provided between an outersurface of the mission case 1 and a tip end portion of a driving arm 15fixedly provided on an outer peripheral surface of the spline tube 5.The shifting actuator 16 has a casing 17 supported in such a way as tobe swingably displaceable with respect to the mission case 1. A shiftingmotor, which is supported by and fixed to the casing 17 and can rotateforwardly and reversely, pushes and pulls the output shaft 18 in anaxial direction through a ball screw mechanism provided in the casing17.

The electric drive apparatus for a transmission changes the gears of thegear unit incorporated in the mission case 1 in the following manner.First, the selecting electric motor 9 is rotated in a predetermineddirection to thereby swing and displace the swinging arm 13 in anup-down direction as viewed in FIG. 7. Then, the shift shaft 2 isaxially displaced in a predetermined direction through the engagementpiece 7 by the engagement convex portion 14 formed on the tip endportion of the swinging arm 13 to thereby perform a selecting operation.After the selecting operation is performed, the shift shaft 2 is rotatedin a predetermined direction through the driving arm 15 by elongatingand contracting the shifting actuator 16 so as to perform a shiftingoperation.

In the case of the aforementioned structure, the base end portion of theswinging arm 13 is connected to an end portion of the output shaft 12through a connecting screw. However, the connecting screw, whichconnects the base end portion of the swinging arm 13 to the end portionof the output shaft 12, may be loosened by prolonged use thereof. Whenthe this swinging arm 13 displaces the shift shaft 2 in an axialdirection, relative displacement of the base end portion of thisswinging arm 13 with respect to the end portion of the output shaft 12occurs in a direction that is slightly opposite to the direction ofrotation of this output shaft 12. This displacement is based on areaction to the operation of displacing the shift shaft 2 in the axialdirection, and caused by the minute gap between inner surfaces of aconcave portion 23, which is formed in the end surface of the outputshaft 12, and both side edges of the base end portion of the swingingarm 13, or by elastic deformation of both side parts of this concaveportion 23.

In either case, when the base end portion of the swinging arm 13displaces with respect to the end portion of the output shaft 12, theconnecting screw, whose head portion abuts against the outer surface ofthis swinging arm 13, tends to displace in the same direction as that inwhich this swinging arm 13 displaces. In the case of the aforementionedstructure, a screw hole, into which the connecting screw is screwed, ispresent in the central portion of the output shaft 12. Thus, theconnecting screw tends to rotate with respect to the screw hole with theprogress of the displacement. This tendency therein to rotate occurs inboth directions as the swinging arm 13 performs reciprocating swingingmotions. However, a force needed for rotating the connecting screw withrespect to the screw hole in a loosening direction is smaller inmagnitude than a force needed for rotating the connecting screw in atightening direction. Therefore, there is the possibility that theconnecting screw is gradually loosened with repetition of thereciprocating swinging motions of the swinging arm 13.

To prevent the connecting screw from being loosened due to theaforementioned causes, it is considered that an engagement portion forpreventing the connecting screw from being loosened is provided betweenthe head portion of this connecting screw and the swinging arm 13.Incidentally, the provision of the engagement portion specifically usedfor preventing the connecting screw from being loosened complicatesprocessing and assembling operations and causes a cost rise.

DISCLOSURE OF THE INVENTION

In view of such circumstances, a swinging actuator of the inventionrealizes a configuration enabled to prevent a screw, which is used forconnecting and fixing the swinging actuator to an output shaft, frombeing loosened.

A swinging actuator of the invention has an output shaft rotatablysupported by a support member, a driving source for rotate-driving theoutput shaft, and an output arm, whose base end portion is connected andfixed to an end surface of the output shaft. A portion to be driven isdriven by the end portion of the output arm. This swinging actuatorcomprises a screw hole provided in a portion, which is positioned offthe center of rotation of the output shaft, a through hole formed in thebase end portion of the output arm, a connecting screw screwed into thescrew hole in a state in which the connecting screw is inserted into thethrough hole, and an engagement portion provided between a part, whichis positioned off the through hole and in the end portion of the outputarm, and a part, which is off the screw hole and in the end surface ofthe output shaft.

In the case of the swinging actuator constituted as described above, thescrew hole is provided in a portion that is off the center of rotationof the output shaft. Thus, a force in the direction of rotation thereofis hard to be applied to the connecting screw, which is screwed into thescrew hole, as a swinging arm performs reciprocating swinging motions.Consequently, even in a case where an engagement portion specificallyused for preventing the connecting screw from being loosened is notprovided therein, the connecting screw is difficult to be loosened.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a front view shoring a selecting actuator according to anembodiment of the invention;

FIG. 2 is a plan view showing the selecting actuator according to theembodiment of the invention;

FIG. 3 is a rear view showing the selecting actuator according to theembodiment of the invention;

FIG. 4 is a side view showing the selecting actuator according to theembodiment of the invention;

FIG. 5 is a cross-sectional view taken along line A-A in FIG. 1;

FIG. 6 is a plan view showing an example of an electric drive apparatusfor a transmission, which incorporates a swinging actuator;

FIG. 7 is a is a cross-sectional view taken along line B-B in FIG. 6;

FIG. 8 is a cross-sectional view taken along line C-C in FIG. 6; and

FIG. 9 is a schematic plan view showing an example of a shift pattern ofa transmission.

BEST MODE FOR CARRYING OUT THE INVENTION

An embodiment of a swinging actuator according to the invention isdescribed in detail. Incidentally, the feature of this embodimentresides in that for the purpose of preventing the connecting screw,which is used for connecting the base end portion of the swinging arm tothe end surface of the output shaft, from being loosened, a structurefor connecting the base end portion of the swinging arm and the endsurface of the output shaft is devised. Hereinafter, this is describedin detail by referring to the accompanying drawings.

FIG. 1 is a front view showing a selecting actuator that is anembodiment of the swinging actuator according to the invention. FIG. 2is a plan view showing the selecting actuator. FIG. 3 is a rear viewshowing the selecting actuator. FIG. 4 is a side view showing theselecting actuator. FIG. 5 is a cross-sectional view taken along lineA-A in FIG. 1.

The selecting actuator according to this embodiment has a casing 19, aselecting electric motor 9 a, which is a driving source assembled to thecasing 19, and an output shaft 12 a assembled to the casing 19. Atransmission shaft 32 provided at an end of a rotation drive shaft 20 ofthe selecting electric motor 9 a is fixedly provided on a pinion gear21, and rotate-drives the coaxially disposed pinion gear 21. The piniongear 21 meshes with a sector gear 22 fixedly provided on the outerperipheral surface of a middle portion of the output shaft 12 a, so thatthe output shaft 12 a can freely be rotate-driven in both directions bya predetermined angle. The transmission shaft 32 and the output shaft 12a are rotatably supported by pairs of ball bearings, respectively, inthe casing 19 in such a way as to be parallel to each other. With theaforementioned configuration, the rotation of the rotation drive shaft20 of the selecting electric motor 9 a is transmitted to the outputshaft 12 a through the transmission shaft 32, the pinion gear 21, andthe sector gear 22.

A screw hole 24 and a latch hole 33 are formed in the end surface (theright end surface as viewed in FIG. 5) of the output shaft 12 a along anaxial direction thereof. The screw hole 24 is a portion, which is offthe center of rotation of the output shaft 12 a, that is, a portionpositioned closer to the outer peripheral surface of the output shaft 12a. On the other hand, the latch hole 33 is formed in a portion, which isa part of the end surface of the output shaft 12 a and shifted from thescrew hole 24 in an opposite direction with respect to the center of theend surface thereof. In other words, the center of the end surfacethereof (the shaft center of the output shaft 12 a) is present in amiddle portion (which is not necessarily a central portion) of astraight line connecting the centers of the screw hole 24 and the latchhole 33.

On the other hand, a through hole 25 and a second through hole 34 areformed in the base end portion of the swinging arm 13 a. The pitchbetween the through hole 25 and the second through hole 34 is equal tothat between the screw hole 24 and the latch hole 33. Therefore, in astate in which the through hole 25 is aligned with the screw hole 24,the latch hole 33 is aligned with the second through hole 34. Further,the second through hole 34 is formed in a portion that is closer to thebase end portion of the swinging arm 13 a than the through hole 25.

The base end portion of the swinging arm 13 a, in which the through hole25 and the second through hole 34 are formed, is connected and fixed tothe end surface of the output shaft 12 a, which has the screw hole 24and the latch hole 33. On connecting therebetween, first, in a state inwhich the latch hole 33 and the second through hole 34 are aligned witheach other, a spring pin is put between both the holes 33 and 34. Inthis state, the spring pin 35 frictionally engages with the innerperipheral surface of one or each of both the holes 33 and 34.Subsequently, a connecting screw 26 inserted into the through hole 25 isscrewed into the screw hole 24 and then tightened securely. In thisstate, a part of a separate washer 36, which is integrally formed with ahead portion 31 of the connecting screw 26 or fitted onto the connectingscrew 26, blocks a part of the second through hole 34. Thus, theslip-off of the spring pin 35 from between both the holes 33 and 34 issurely prevented. An ordinary pin having no elasticity may be used as amember put between both the holes 33 and 34.

An engagement convex portion 14 a is fitted and fixed to the end portionof the swinging arm 13 a. The engagement convex portion 14 a isconstituted in such a manner as to be engageable with an engagementpiece 7 (see FIGS. 6 and 7) fixed to the shift shaft 2.

In the casing 19, a displacement sensor 27 is supported coaxially withthe output shaft 12 a. An engagement projection 29, which is provided ona detection portion 28 of this displacement sensor 27 in such a way asto protrude therefrom, engages with an engagement concave portion 30formed in the base end part of the detection portion 28. Thedisplacement sensor 27 is constituted like a potentiometer, whoseelectric characteristics, such as values of resistance, change accordingto an angle of rotation of the detection portion 28, and enabled todetect a swinging angle of the output shaft 12 a.

In a case where the shift shaft 2 shown in FIG. 6 is displaced in theaxial direction by the selecting actuator 8 a, the pinion gear 21 isrotated in a predetermined direction by driving the selecting electricmotor 9 a. The output shaft 12 a is turned by the rotation of the piniongear 21 through the sector gear 22. Thus, the swinging displacement ofthe swinging arm 13 a is caused. Then, the engagement convex portion 14a provided at the end portion of this swinging arm 13 a displaces theshift shaft 2 in the axial direction. Then, the displacement sensor 27detects a displacement magnitude as an angle of rotation of the outputshaft 12 a.

As described above, according to this embodiment, in a state in whichthe base end portion of the swinging arm 13 a is connected and fixed tothe end surface of the output shaft 12 a, torque is transmitted from theoutput shaft 12 a to the swinging arm 13 a. Regardless of minuteswinging displacement of he base end portion of the swinging arm 13 awith respect to the end portion of the output shaft 12 a, which iscaused by this transmission of torque, the connecting screw is preventedfrom being loosened.

That is, similarly, in this embodiment, the transmission of torquecauses the minute relative displacement of the base end portion of theswinging arm 13 a around the shaft center of the output shaft 12 a withrespect to the end portion of the output shaft 12 a in a directionopposite to the direction of rotation of this output shaft 12 a. In thecase of this embodiment, the screw hole 24, into which the connectingscrew 26 is screwed, is provided in the portion that is positioned offthe shaft center of the output shaft 12 a. Thus, with the minutedisplacement, a force in a direction of rotation of the connecting screw26 is hard to be applied to the connecting screw 26 screwed into thescrew hole 24. Consequently, even when an engagement portionspecifically used for preventing the connecting screw from beingloosened is not provided, the connecting screw 26 is hard to beloosened.

Incidentally, according to this embodiment, the position of the screwhole 24, in which the connecting screw 26 is screwed, is devised.Consequently, the connecting screw 26 is prevented from being loosened.The structure for preventing an occurrence of the relative rotation ofthe swinging arm 13 a around the connecting screw 26 with respect to theoutput shaft 12 a is not limited to the spring pin 35. Variousstructures, which have hither to be known, may be employed.Incidentally, in the case of the structure implemented by the engagementbetween a pin and a hole can reduce the cost, because of easiness ofprocessing each of the parts.

Although the embodiment according to the invention has been described inthe foregoing description, it is apparent to those skilled in the artthat various alterations and modifications may be made without departingfrom the spirit and scope of the invention.

The present application is based on the Japanese Patent Application (No.2002-031248), filed Feb. 7, 2000, the contents of which are incorporatedby reference.

Industrial Applicability

A highly reliable and low cost swinging actuator can be obtained.

1. A swinging actuator having an output shaft rotatably supported by asupport member, a driving source for rotate-driving said output shaft,and an output arm, whose base end portion is connected and fixed to anend surface of said output shaft, a portion to be driven being driven bysaid end portion of said output arm, said swinging actuator,characterized by comprising: a screw hole provided in a portion, whichis positioned off a center of rotation of said output shaft; a throughhole formed in said base end portion of said output arm; a connectingscrew screwed into said screw hole in a state in which said connectingscrew is inserted into said through hole; and an engagement portionprovided between a part, which is positioned off said through hole andin said end portion of said output arm, and a part, which is off saidscrew hole and in said end surface of said output shaft.
 2. The swingingactuator according to claim 1, wherein a shaft center of said outputshaft is positioned between said connecting screw and said engagementportion.